The White House has confirmed that a jihadist video showing the beheading of American journalist James Foley is authentic.

The Islamic State (IS) group released the video on Tuesday, saying Foley's killing was revenge for US air strikes on its fighters in Iraq.

The US, UK and France have expressed abhorrence at the video.

Foley's mother Diane said he "gave his life trying to expose the world to the suffering of the Syrian people."

President Barack Obama is due to give a statement later.

Foley, 40, has reported extensively across the Middle East, working for US publication GlobalPost and other media outlets including French news agency AFP.